Abstract:

Process for preparing polyurethanes having an Asker C hardness of from 1
to 70 by reacting (a) isocyanates with (b) compounds which are reactive
toward isocyanates, wherein (b1) monools which have a molecular weight in
the range from 1500 g/mol to 6000 g/mol and are based on monoalcohols
having from 2 to 6 carbon atoms which have been alkoxylated by means of
ethylene oxide and/or propylene oxide are used as (b) compounds which are
reactive toward isocyanates.

Claims:

1. A process for preparing polyurethanes having an Asker C hardness of
from 1 to 70 by reacting (a) isocyanates with (b) compounds which are
reactive toward isocyanates, wherein (b1) monools which have a molecular
weight in the range from 1500 /mol to 6000 g/mol and are based on
monoalcohols having from 2 to 6 carbon atoms which have been alkoxylated
by means of ethylene oxide and/or propylene oxide are used as (b)
compounds which are reactive toward isocyanates.

2. The process according to claim 1, wherein the weight ratio of ethylene
oxide to propylene oxide is from 20:80 to 80:20, with the different
alkylene oxides being able to be arranged in blocks and/or randomly.

3. The process according to claim 1, wherein (b1) is based on 1-butanol
which has been alkoxylated by means of ethylene oxide and propylene
oxide.

4. The process according to claim 1, wherein at least one compound (b)
which is reactive toward isocyanates and has a functionality toward
isocyanates of at least two and a molecular weight in the range from 1500
to 8000 g/mol is used in addition to (b1)

5. The process according to claim 4, wherein the proportion by weight of
(b1) in (b) is from 10% by weight to 80% by weight, based on the total
weight of (b) including (b1).

6. The process according to claim 1, wherein a prepolymer which bears
isocyanate groups and is based on the reaction of isocyanates, with
monools (b1i) which have a molecular weight in the range from 1500 g/mol
to 6000 g/mol and are based on monoalcohols having from 2 to 6 carbon
atoms which have been alkoxylated by means of ethylene oxide and/or
propylene oxide, is used as isocyanate (a).

7. The process according to claim 6, wherein the prepolymer bearing
isocyanate groups is based on the reaction of isocyanates, with monools
(b1i) which have a molecular weight in the range from 1500 g/mol to 6000
g/mol and are based monoalcohols having from 2 to 6 carbon atoms which
have been alkoxylated by means of ethylene oxide and/or propylene oxide
and also, in addition to (b1i) at least one compound (bi) which is
reactive toward isocyanates and has a functionality toward isocyanates of
at least two and a molecular weight in the range from 1500 to 8000 g/mol.

8. The process according to claim 7, wherein the proportion by weight of
(b1i) in (bi) is from 10% by weight to 80% by weight, based on the total
weight of (bi) including (b1i).

9. A polyurethane obtainable by a process according to claim 1.

Description:

[0001]The invention relates to a process for preparing polyurethanes,
preferably polyurethane elastomers, particularly preferably compact
polyurethane elastomers, which have an Asker C hardness of from 1 to 70,
preferably from 5 to 25, and preferably contain no customary plasticizers
by reacting (a) isocyanates with (b) compounds which are reactive toward
isocyanates. Furthermore, the invention relates to polyurethanes having
an Asker C hardness of from 1 to 70, preferably from 5 to 25, which can
be obtained in this way and also products, in particular moldings for
shoes, bicycle saddles or moldings for orthopedic technology comprising
these polyurethanes according to the invention.

[0003]Polyurethanes containing liquid plasticizers are known in the
production of pliable moldings having an Asker C hardness of less than
70, e.g. for insoles or as soft-feel computer keyboards, The plasticizers
are usually required both for setting the desired hardness and as
diluents for the generally highly viscous polyester polyols. However, the
use of plasticizers is undesirable because of their migration properties.
In addition, the known solutions have the disadvantage that the moldings
tend to be very sticky on the surface, in particular in the case of
reaction systems which require a relatively long reaction time for
curing.

[0005]It was an object of the present invention to develop a process for
preparing polyurethanes, preferably a polyurethane gel, which have an
Asker C hardness of from 1 to 70, preferably from 5 to 25, and preferably
contain no customary plasticizers and are only slightly sticky and
virtually odor-free, in which the softness can be achieved without use of
plasticizers, have a pleasant touch, are washable and when used as
pressure sensitive adhesive can easily be removed from the substrate.
This object has been able to be achieved by using (b1) monools which have
a molecular weight in the range from 1500 g/mol to 6000 g/mol, preferably
from 1900 g/mol to 4000 g/mol, and are based on monoalcohols having from
2 to 6 carbon atoms, preferably from three to five carbon atoms, which
have been alkoxylated by means of ethylene oxide and/or propylene oxide,
preferably ethylene oxide and propylene oxide, as (b) compounds which are
reactive toward isocyanates.

[0007]The weight ratio of ethylene oxide to propylene oxide in the monool
(b1) is preferably from 20:80 to 80:20, particularly preferably from
40:60 to 60:40, with the different alkyene oxides being able to be
arranged in blocks and/or randomly,

[0008]Particular preference is given to (b1) being based on 1-butanol
which has been alkoxylated, preferably randomly, by means of ethylene
oxide and propylene oxide.

[0009]The polyurethane gels of the invention are preferably used in
plasticizer-free components such as mouse pads, bicycle saddles, insoles
various handles or grips.

[0010]Apart from the applications mentioned, the polyurethanes of the
invention are also suitable for producing elastic computer keyboards or
consumer art ices of a similar type and also in the fields of
intensive-care medicine, e.g. for the production of special beds, or
vehicle technology where very pliable moldings are required. Particular
preference is given to moldings having this low hardness for applications
in the shoe and othopedics sector. Thus, very soft to gel-like insoles
which have particularly favorable support properties can be produced
using the pliable PUR cast resin system. In orthopedics, the novel
property of the PUR cast resin system of the invention is particularly
advantageous. Thus, the cured novel system or the finished moldings has
gas solvent properties under pressure. Thus, very soft to gel-like
insoles can be produced using the polyurethanes of the invention, with
the starting components being able to be loaded with (a) gas, e.g. air or
nitrogen, for preparing the polyurethanes This loading with air can be
carried out by generally known methods using customary machines, for
example high-pressure machines. When such a sole provided with
microbubbles is used in the shoe, an imprint of the pressure lading and
pressure distribution is obtained after he shoe has been worn for a
certain time, since the gas in the microbubbles dissolves in the region
of pressure loading and the sole becomes transluscent to clear in these
places. Accordingly, the polyurethanes of the invention, in particular
shoe components and in particular shoe soles, which have gas bubbles,
preferably air bubbles, having a diameter of from 5 to 500 mm in the
polyurethane are also preferred according to the invention. Preference is
given according to the invention to polyurethanes which have a compact
structure or, owing to loading with gases, have gas bubbles having the
abovementioned diameter, particularly preferably compact polyurethanes.

[0011]These products, in particular bicycle saddles, moldings for the shoe
and orthopedic sectors, comprising the polyurethanes of the invention are
thus likewise provided by the present invention.

[0012]Particular preference is also given to adhesive elements, in
particular pressure sensitive and adhesive strips, comprising the
polyurethanes of the invention.

[0013]The production of the polyurethanes of the invention can be carried
out by generally known methods, in particular methods which are known for
cast resin systems, for example by mixing the starting components and
curing of the reaction mixture in appropriate molds. The processing to
form the shaped part can in the simplest case be carried out by manual
mixing of the components. However, preference is given to machine
processing which can be carried out either by means of a low-pressure
polyurethane processing machine or by means of a high-pressure
polyurethane processing machine. Under the latter processing conditions,
the starting components according to the invention can be processed
without problems at component temperatures of up to 90° C. and
pressures of up to 200 bar.

[0014]The production of polyurethanes, usually on the basis of (a)
isocyanates and (b) compounds which are reactive toward isocyanates and,
if appropriate, (C) catalysts, (d) blowing agents, (e) gases and/or (f)
auxiliaries, is generally known and has been described widely.

[0015]The following details regarding the starting components nay be
provided:

[0016]As (a) isocyanates, preferably organic diisocyanates and/or
polyisocyanates, it is possible to use the aliphatic, cycloaliphatic,
araliphatic and preferably aromatic polyfunctional isocyanates known per
se. Specific examples are: alkylene diisocyanates having from 4 to 12
carbon atoms in the alkylene radical, e.g. dodecane
1,12-diisocyanate,2-ethyltetramethylene-1,4-diisocyanate,
2-methylpentamethylene 1,5-diisocyanate, tetramethylene 1,4-diisocyanate
and preferably hexamethylene 1,6-diisocyanate; cycloaliphatic
diisocyanates such as cyclohexane 1,3- and 1,4-diisocyanate and also any
mixtures of these isomers,
1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophorone
diisocyanate), hexahydrotolylene 2,4- and 2,6-diisocyanate and also the
corresponding isomer mixtures, dicyclohexylmethane 4,4'-2,2'- and
2,4'-diisocyanate and also the corresponding isomer mixtures, and
preferably aromatic diisocyanates and polyisocyanates such as tolylene
2,4- and 2,6-diisocyanate and the corresponding isomer mixtures,
diphenylmethane 4,4'-, 2,4'- and 2,2'-diisocyanate and the corresponding
isomer mixtures, mixtures of diphenylmethane 4,4'- and
2,4'-diisocyanates, polyphenylpolymethylene polyisocyanates, mixtures of
diphenylmethane 4,4'-, 2,4'- and 2,2'-diisocyanates and
polyphenylpolymethylene polyisocyanates (crude MDI) and mixtures of crude
MDI and tolylene diisocyanates. The organic diisocyanates and
polyisocyanates can be used individually or in the form of their
mixtures. Use is frequently also made of modified polyfunctional
isocyanates, i.e. products obtained by chemical reaction of organic
diisocyanates and/or polyisocyanates. Examples which may be mentioned are
diisocyanates and/or polyisocyanates containing ester, urea, biuret,
allophanate, carbodiimide, isocyanurate, uretdione and/or urethane
groups. Specific examples are: organic, preferably aromatic
polyisocyanates containing urethane groups and having NCO contents of
from 33.6 to 15% by weight, preferably from 31 to 21% by weight, based on
the total weight, for example diphenylmethane 4,4'-diisocyanate modified
with low molecular weight diols, triols, dialkylene glycols, trialkylene
glycols or polyoxyalkylene glycols having molecular weights up to 6000,
in particular molecular weights up to 1500, modified diphenylmethane
4,4'- and 2,4'-diisocyanate mixtures or modified crude MDI or tolylene
2,4- or 2,6-diisocyanate, with examples of dialkylene glycols or
polyoxyalkylene glycols which can be used individually or as mixtures,
being: diethylene glycol, dipropylene glycol, polyoxyethylene,
polyoxypropylene and polyoxypropylene-polyoxyethylene glycols, triols
and/or tetrols. Also suitable are prepolymers which contain NCO groups
and have NCO contents of from 25 to 3.5% by weight, preferably from 21 to
14% by weight, based on the total weight, and are prepared from the
polyester polyols and/or preferably polyether polyols described below and
diphenylmethane 4,4'-diisocyanate, mixtures of diphenylmethane 2,4'- and
4,4'-diisocyanate, tolylene 2,4- and/or 2,6-diisocyanates or crude MD.
Further isocyanates which have been found to be useful are liquid
polyisocyanates containing carbodiimide groups and/or isocyanurate rings
and having NCO contents of from 33.6 to 1% by weight, preferably from 31
to 21% by weight, based on the total weight, e.g. ones based on
diphenylmethane 4,4'-, 2,4'-and/or 2,2'-diisocyanate and/or tolylene 2,4-
and/or 2,6-diisocyanate. The modified polyisocyanates can, if
appropriate, be mixed with one another with unmodified organic
polyisocyanates such as diphenylmethane 2,4'-, 4,4'-diisocyanate, crude
MDI, tolylene 2,4- and/or 2,6-diisocyanate. Organic polyisocyanates which
have been found to be particularly useful and are therefore preferably
employed are: mixtures of tolylene diisocyanates and crude MDI or
mixtures of modified organic polyisocyanates containing urethane groups,
in particular those based on tolylene diisocyanates, diphenylmethane
4,4'-diisocyanate, diphenylmethane diisocyanate isomer mixtures or crude
MDI, in particular crude MDI having a diphenylmethane diisocyanate isomer
content of from 30 to 80% by weight, preferably from 30 to 55% by weight.
Preference is given to using a urethane-modified isocyanate which has an
NCO content of less than 15%, particularly preferably a urethane-modified
isocyanate which is the reaction product of an isocyanate with a
polyether diol having a molecular weight of at least 1000 g/mol,
preferably from 2000 to 6000 g/mol, particularly preferably with a
mixture of a bifunctional polyether polyol based on propylene glycol,
propylene oxide and ethylene oxide and having a molecular weight of
greater than 2000 g/mol and a polypropylene glycol having a molecular
weight of greater than 1000 g/mol, as (a) isocyanates.

[0017]Particular preference is given to using a prepolymer which bears
isocyanate groups and is based on the reaction of isocyanates, preferably
diisocyanates, with monools (b1i) which have a molecular weight in the
range from 1500 g/mol to 6000 g/mol, preferably from 1900 g/mol to 5000
g/mol, particularly preferably from 3000 g/mol to 4500 g/mol, and are
based on monoalcohols having from 2 to 6 carbon atoms which have been
alkoxylated by means of ethylene oxide and/or propylene oxide as
isocyanate (a). The prepolymer bearing isocyanate groups is very
particularly preferably based on the reaction of isocyanates, preferably
diisocyanates, with monools (b1i) which have a molecular weight of from
1500 g/mol to 6000 g/mol, preferably from 1900 g/mol to 5000 g/mol,
particularly preferably from 3000 g/mol to 4500 g/mol, and are based on
monoalcohols having from 2 to 6 carbon atoms which have been alkoxylated
by means of ethylene oxide and/or propylene oxide and also in addition to
(b1i) at least one compound (bi), preferably polyether alcohol, which is
reactive toward isocyanates and has a functionality toward isocyanates of
at least two, preferably from 2 to 4, particularly preferably 2 or 3, in
particular 2, and a molecular weight in the range from 1500 to 8000
g/mol, The proportion by weight of (b1i) in (bi) is from 10% by weight to
80% by weight, based on the total weight of (bi) including (b1i). The
compounds (b1) presented at the outset can be used as (b1i). As compounds
(bi), it is possible to use the compounds (b) described in this text. The
distinction in the labeling between (b1i) and (b1) and between (b) and
(bi) is made merely to relate the preferred quantities of the components
(b1) and (b) separately to the polyol component (b) or the isocyanate
component (a), respectively.

[0018]In addition to the monools (b1) used according to the invention, it
is possible to use further isocyanate-reactive compounds (b) which have
at least two reactive hydrogen atoms, advantageously compounds having a
functionality of from 2 to 8, preferably from 2 to 6, and a molecular
weight of from 500 to 9000 g/mol. Compounds of this type which have been
found to be useful are, for example, polyetherpolyamines and/or
preferably polyols selected from the group consisting of polyether
polyols, polyester polyols, polythioether polyols, hydroxyl-containing
polyesteramides, hydroxyl-containing polyacetals and hydroxyl-containing
aliphatic polycarbonates and mixtures of at least two of the polyols
mentioned. Preference is given to using polyester polyols and/or
polyether polyols. The polyetherols are usually prepared by addition of
lower alkylene oxides, in particular ethylene oxide and/or propylene
oxide, onto starter substances having a functionality of from 2 to 8, in
particular from 2 to 6. Suitable polyester polyols can be prepared, for
example, from organic dicarboxylic acids having from 2 to 12 carbon
atoms, preferably aliphatic dicarboxylic acids having from 4 to 6 carbon
atoms, and polyhydric alcohols, preferably diols having from 2 to 12
carbon atoms, preferably 2 to 6 carbon atoms. Possible dicarboxylic acids
are, for example: succinic acid, glutaric acid, adipic acid, suberic
acid, azelaic acid, sebacic acid, decanedicarboxylic acid, maleic acid,
fumaric acid, phthalic acid, isophthalic acid and terephthalic acid. The
dicarboxylic acids can be used either individually or in admixture with
one another. In place of the free dicarboxylic acids, it is also possible
to use the corresponding dicarboxylic acid derivatives, e.g. dicarboxylic
monoesters and diesters of alcohols having from 1 to 4 carbon atoms or
dicarboxylic anhydrides. Preference is given to using dicarboxylic acid
mixtures of succinic, glutaric and adipic acids in weight ratios of, for
example, 20-35:35-50:20-32, and in particular adipic acid, Examples of
dihydric and polyhydric alcohols, in particular alkanediols and
dialkylene glycols, are: ethanediol, diethylene glycol, 1,2- or
1,3-propanediol, dipropylene glycol, 1,4-butanediol, 1,5-pentanediol,
1,6-hexanediol, 1,10-decanediol, glycerol and trimethylolopropane.
Preference is given to using ethanediol, diethylene glycol,
1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol or mixtures of at least
two of the diols mentioned, in particular mixtures of 1,4-butanediol,
1,5-pentanediol and 1,6-hexanediol. It is also possible to use polyester
polyols derived from lactones, e.g. ε-caprolactone, or
hydroxycarboxylic acids, e.g. Ω-hydroxycaproic acid. The polyester
polyols preferably have a functionality of from 2 to 4, in particular
from 2 to 3, and a molecular weight of from 500 to 3000 g/mol, preferably
from 1200 to 3000 g/mol and in particular from 1800 to 2500 g/mol. The
molecular weights indicated in this text are the number average molecular
weights in [g/mol]. Preference is given to using at least one
isocyanate-reactive compound (b), preferably a polyether alcohol, which
has a functionality toward isocyanates of at least 2, preferably from 2
to 4, particularly preferably 2 or , in particular 2, and a molecular
weight in the range from 1500 to 8000 g/mol, preferably from 1900 g/mol
to 4000 g/mol, in addition to (b1). The proportion by weight of (b1) in
(b) is in this case preferably from 10% by weight to 80% by weight, based
on the total weight of (b) including (b1).

[0019]It is also possible to use further diols and/or triols having
molecular weights of less than 499 g/mol, preferably from 60 to 300
g/mol, as (b). Suitable compounds of this type are, for example,
aliphatic, cycloaliphatic and/or araliphatic diols having from 2 to 14,
preferably from 4 to 10, carbon atoms, e.g. ethylene glycol,
1,3-propanediol, 1,10-decanediol, o-, m-, p-dihydroxycyclohexane,
diethylene glycol, dipropylene glycol and preferably 1,4-butanediol,
1,6-hexanediol and bis(2-hydroxyethyl)hydroquinone, triols such as
1,2,4-, 1,3,5-trihydroxcyclohexane, glycerol and trimethylolpropane and
low molecular weight hydroxyl-containing polyalkylene oxides based on
ethylene oxide and/or 1,2-propylene oxide and the abovementioned diols
and/or triols as starter molecules.

[0020]As catalysts (c) for producing the polyurethanes, it is possible to
use, in particular, compounds which strongly accelerate the reaction of
the compounds containing reactive hydrogen atoms, in particular hydroxyl
groups, with the organic, optionally modified polyisocyanates. Possible
catalysts are organic metal compounds, preferably organic tin compounds
such as tin(II) salts of organic carboxylic acids, e.g. tin(II) acetate,
tin(II) octoate, tin(II) ethylhexanoate and tin(II) laurate, and the
dialkyltin(IV) salts of organic carboxylic acids, e.g. dibutyltin
diacetate, dibutyltin dilaurate, dibutyltin maleate and dioctyltin
diacetate. The organic metal compounds are used alone or preferably in
combination with strongly basic amines. Amines which may be mentioned
are, for example, amidines such as
2,3-dimethyl-3,4,5,6-tetrahydropyrimidine, tertiary amines such as
triethylamine, tributylamine, dimethylbenzyiamine, N-methylmorpholine,
N-ethylmorpholine, N-cyclohexylmorpholine,
N,N,N',N'-tetramethylethylenediamine, N,N,N',N'-tetramethylbutanediamine,
N,N,N',N'-tetramethylhexane-1,6-diamine, pentamethyldiethylenetriamine,
bis(dimethylaminoethyl) ether, bis(dimethylaminopropyl)urea,
dimethylpiperazine, 1,2-dimethylimidazole, 1-azabicyclo[3.3.0]octane and
preferably 1,4-diazabicyclo[2.2.2]-octane, and alkanolamine compounds
such as triethanolamine, triisopropanolamine, N-methyldiethanolamine and
N-ethyldiethanolamine and dimethylethanolamine. Further suitable
catalysts are: tris(dialkylaminoalkyl)-s-hexahydrotriazines, in
particular tris(N,N-dimethylaminopropyl)-s-hexahydrotriazine,
tetraalkylammonium hydroxides such as tetramethylammonium hydroxide,
alkali metal hydroxides such as sodium hydroxide and alkali metal
alkoxides such as sodium methoxide and potassium isopropoxide, and also
alkali metal salts of long-chain fatty acids having from 10 to 20 carbon
atoms and possibly lateral OH groups. Preference is given to using from
0.001 to 5% by weight, in particular from 0.05 to 2% by weight, of
catalyst or catalyst combination, based on the weight of the polyol
component.

[0021]As blowing agents (d) for the polyurethane systems employed, it is
possible to use the blowing agents customary for the production of
polyurethane foams, for example halogenated alkanes. Low-boiling
aliphatic hydrocarbons, preferably cyclopentane, n-pentane and/or
isopentane, in particular n-pentane, are advantageously used as physical
blowing agents. It is advantageous to use the aliphatic hydrocarbons
together with water as blowing agent. The amount of aliphatic
hydrocarbons used is, for example, from 2 to 25% by weight, preferably
from 10 to 13% by weight, based on the polyol component. The proportion
of water depends on the desired properties of the polyurethane.
Preference is given to using no blowing agent.

[0022]If appropriate, auxiliaries f) can also be incorporated into the
polyurethane system. Examples which may be mentioned are surface-active
substances, cell regulators, fillers, dyes, pigments, flame retardants,
hydrolysis inhibitors, fungistatic and bacteriostatic substances.

[0023]The invention is illustrated by the following examples:

TABLE-US-00001
[% by weight]
Polyol component
Polyol 1: 1.00
Polyol 2: 40.65
Monool 1: 58.00
Coscat ® 83) 0.35
Isocyanate component
Polyol 3: 23.08
Monool 2: 38.46
4,4'-MDI, 2,4'-MDI (1:1) 38.46
Mixing Ratio: Component A/B = 100/20 - 30
Polyol 1: Polyether polyol having a functionality of 4 and a molecular
weight of 300 g/mol, initiated by means of ethylenediamine and
propoxylated with PO;
Polyol 2: Polyether polyol having a nominal functionality of 3 and a
molecular weight of 5000 g/mol, initiated by means of glycerol and
propoxylated with PO and end-capped with 13.3% of EO
Polyol 3: Polyether polyol having a functionality of 3 and a molecular
weight of 3000 g/mol, initiated by means of glycerol and propoxylated and
ethoxylated with PO/EO (95.4:4.6) and end-capped with 5.8% of EO
Coscat ® 83: Bismuth trisneodecanoate (58%) in 42% of neodecanoic
acid, procured from Caschem
Monool 1: Polyetherol having a molecular weight of 2000 g/mol and based
on 1-butanol and ethylene oxide and propylene oxide in a ratio of 1:1
with random distribution;
Monool 2: Polyetherol having a molecular weight of 3850 g/mol and based
on 1-butanol and ethylene oxide and propylene oxide in a ratio of 1:1
with random distribution

[0024]The product had the advantages presented at the outset (slightly
sticky, virtually odorless, softness without use of plasticizers,
pleasant touch, washable and when used as pressure sensitive adhesive is
easy to remove from the substrate) has an Asker C hardness of about 5-10,
has a high elongation (250%) is reversibly deformable and sticks to
substrates of many different types (e.g. wood, glass, metals, most
plastics) from which it can be pulled off again without being destroyed.
The tensile strength is 0.06 N/mm2, and the tear propagation
resistance is 0.13 N/mm2 .